6VDC Golf Cart Battery Question

I am redoing my house battery situation (it currently comes off the start batteries). I understand that you have to hook 2 of the 6Vdc batteries in series to achieve 12vdc, then when adding additional banks you connect them in parallel. So now I have 2 12Vdc banks, each bank has 4-6Vdc batteries. Each bank has a positive and negative wires for the 12vDC connection to the house. Already have the positive wire figured out as it is already provided.
Question:

Where do you connect the negative (ground) wire on the bank? Hook it to a negative post on the start battery or ground point on the engine?

Either connection might work as long as the house loads somehow ground to them.

But it would be better to look at where your house loads connect their grounds. Often there is a buss that these grounds come back to and you connect that buss to the negative terminal of the house batteries. That should be a more direct ground path.

But why two house banks. It is better to wire them as one big bank.

David

djmarchand said:

But why two house banks. It is better to wire them as one big bank.

David

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Depends on how you plan to charge it or them.

When I did ours, I used several BusBars to manage all the connections to avoid stacking too many onto battery posts. https://www.bluesea.com/products/category/BusBars/PowerBar

There is some discussion both ways as to using the engine block as a grounding point for the house bank. You have to for the starter battery anyway, just to finish the loop to the starter motor. However, if you are going to be able to combine house and start for whatever reason, the house ground will need to find its way to the block at some point for that to work. So I used a busbar and then took a very heavy gauge wire to a solid ground on the block.

Good points all.

I plan on two banks, with 4-6Vdc batteries in each bank. The reason for this is because of the way the boat manufacture wired it. On my DC panel I have a battery switch (as most of us do) with a Off, #1, #2 and both. In the engine bay where my batteries are located, I have two red heavy gage wires for the house, one for #1 and the other is #2. Both #1 and #2 run ALL of the DC needs on the boat doesn't matter if the switch is selected for #1 or #2 all DC is powered. Placing the switch to both will just increase my amp hours as I am now tying in both banks.

As far as charging, the banks will be charged two different ways. The first will be a battery charger. I have one that is a 3 bank charger, but will only be using two legs. My start batteries will not be on the charger as there is no need to as I start and run my boat all the time, thus charging the start battery.

The second way the house bank will be charged is when the engines are running as I am installing a two engine battery isolator.

Good point on the ground to the engine block in case I have to jump start from the house batteries. I believe this is the way it is currently set up. I also think the two start batteries are tied together with the ground between the two batteries and then each battery is grounded to the engine starter.

Normal battery isolators have a forward voltage drop of a half volt or so. This voltage drop means that there is not enough voltage at the batteries for efficient charging.

Look at the FET isolators by Victron here- Argo FET Battery Isolators - Victron Energy

They have a very low voltage drop and eliminate this problem

OTOH I am a big fan of battery combiners for this purpose. Look at Yandina Marine Electronics

David

Thanks david. Good info!

djmarchand said:

Normal battery isolators have a forward voltage drop of a half volt or so. This voltage drop means that there is not enough voltage at the batteries for efficient charging.

Look at the FET isolators by Victron here- Argo FET Battery Isolators - Victron Energy

They have a very low voltage drop and eliminate this problem

OTOH I am a big fan of battery combiners for this purpose. Look at Yandina Marine Electronics

David

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I wouldn't even consider a battery isolator of any kind. Battery combiners are much more efficient. In addition to Yandina, many other companies make these, often calling them automatic charging relays (ACR).

Folks in the know with battery isolators and capable charging systems can adjust their charging systems to accommodate that 0.5-1.0 V loss during charging. I know folks here who have done just that. At the time, I didn't have a charging system capable of adjustment, so I installed a Yandina combiner. Blue Sea also makes quality ACRs.

I am also in the process of doing some rewiring of batteries / alt / charger and agree w/ the comments so far...

I am wondering why you wouldn't use the third bank on the charger to keep the starting battery at full charge? Most smart chargers today do a better job at fully charging than the alternator does (I believe)

Most of the combiners / ACT's recommend wiring the alternator primary to the largest bank (house) and then connecting to the start batty.
The attached shows the recommended hookup for parallel batteries / banks - I'm not sure exactly why but I have seen references that state this will charge & discharge more evenly and improve performance & life.

Don
2008 Mainship 34 HT Trawler
Bacchus

I agree, Don, but I have split my loads and charges to provide complete control of both at all times. There is no shared cabling between the two as there was when I purchased the boat.

Assuming each battery depicted in your diagram represents a series-connected pair of 6V GC batts, that's how loads are connected. I run all my loads through 1-ALL-2-OFF switches outside the ER before they connect to any buses to allow me to select, isolate and share loads.

I am configured differently for my charge currents. In my twin engine/alternator boat, I have the high output alt connected directly to the house bank and the smaller stock alt connected directly to the start batt. My single-bank charger is connected to the house bank with a switched Yandina combiner to share the charge with the start batt when needed.

Bacchus said:

I am wondering why you wouldn't use the third bank on the charger to keep the starting battery at full charge? Most smart chargers today do a better job at fully charging than the alternator does (I believe)

Don
2008 Mainship 34 HT Trawler
Bacchus

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Hey Don,

There is no need to have a charger connected to the start batteries. I start and run my boat a lot, so the start batteries are always charged full, thus no need to charge them.

I like the old oil pressure activated switch connected to a charger relay for tying the engine alternator to the house bank. Simple.

An oil pressure switch Is simple , BUT you are not in charge.

With the charge solenoid wired to the ACC position on a key switch , you can once a month place it in acc while dockside and charge the start batt.

Starts age and loose internally , like every batt , so after a few weeks or a month dockside it will live longer being recharged.

Why would anyone not take advantage of the technology of the battery combiners or automatic charging relays commonly and inexpensively available?

No need to remember anything no need to switch anything.

You don't always want the start battery taking the charge being provided to the house bank or it can overcharge resulting in excessive water loss.

For me, a switchable combiner is the best of both worlds. YMMV

>Why would anyone not take advantage of the technology of the battery combiners or automatic charging relays commonly and inexpensively available?

No need to remember anything no need to switch anything.<

RVs have been doing this since 1950 , with an $18 buck relay.

>You don't always want the start battery taking the charge being provided to the house bank or it can overcharge resulting in excessive water loss. <

I dont think so. Start batts in todays cars and trucks are used with the alt charging almost all the time.

Lights , blowers, hot seats,boom boxes and the rest mean most cars are at 14+ volts as the numerous users draw juice.

A good 3 stage V regulator will bring the house to 14.4 (or so) before cutting back to float.

No harm with a batt created to operate 99% of the time at 14V + in overcharging.

Alaskan Sea-Duction said:

Hey Don,

There is no need to have a charger connected to the start batteries. I start and run my boat a lot, so the start batteries are always charged full, thus no need to charge them.

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Not always the case. Many vessels, mine included, have separate chargers for the engine start batteries. Why not? Redundancy is great with the availability of the start battery charger to charge the house bank if the inverter charger for some reason not performing.

In my case the dinghy davit is powered from the engine starts. To monitor the health of engine starts we have a separate Magnum BMK.

sunchaser said:

Not always the case. Many vessels, mine included, have separate chargers for the engine start batteries. Why not? Redundancy is great with the availability of the start battery charger to charge the house bank if the inverter charger for some reason not performing.

In my case the dinghy davit is powered from the engine starts. To monitor the health of engine starts we have a separate Magnum BMK.

Click to expand...

Good point. I don't have any inverters (yet). My battery charger is a fairly new one, with 3 legs. I also have a portable charger onboard just in case and that is powered when I run the genny.

I guess I dont understand why you would not want to charge everything when the main (s) are running. Typically the main is incredibly inefficient so loading up the alternator can only help. I have a pair of 250 amp 24 volt 50DNs in an attempt to get more load at low rpm.

My alternators are appropriately sized for the battery banks receiving the charges while underway. I isolate my start battery from the charge being received by the house bank in a few circumstances:

1. If I come into a marina with a hungry house bank and a full start battery, I'll leave the start battery isolated to prevent overcharging of the start batt while the house gets its needed bulk and absorption charges.

2. When I'm underway, my twin alternators provide the charge needed to each battery bank independently. Usually, there is no need to combine them.

3. If my start battery is fully charged at the home marina and I'm planning to head back out within a week or so, I can leave the banks separated so the single bank shore charger just charges the house bank. It probably wouldn't hurt getting a float charge, but it's also not really needed for that short period. On the other hand, my house bank almost always needs a charge when I return home so it gets what it needs from the shore charger in my absence.

I have a pair of 250 amp 24 volt 50DNs in an attempt to get more load at low rpm.

These will only help IF you installed a 3 or 4 stage V regulator .

The stock bus unit will not charge very hard a discharged bat set.

It will only charge 50% of what is needed to fill the batts at any time.

Fine when the set is low , but stinks when you are at 80% and its charging very little.

AS the 50DN are powerful be sure to get a batt thermometer with the better V reg.

kulas44 said:

I guess I dont understand why you would not want to charge everything when the main (s) are running. Typically the main is incredibly inefficient so loading up the alternator can only help. I have a pair of 250 amp 24 volt 50DNs in an attempt to get more load at low rpm.

Click to expand...

No no no. When the mains are running, everything that needs a charge will get charged.

Well thought I would close this out. Finished the install. Still have 4 more batteries to buy, buy all the wiring is done. With the four batteries and 2 banks I have 840 amp hours which will increase to 1680 Ah when I buy the other batteries. Check out my blog for more pics.

Alaskan Sea-Duction said:

Well thought I would close this out. Finished the install. Still have 4 more batteries to buy, buy all the wiring is done. With the four batteries and 2 banks I have 840 amp hours which will increase to 1680 Ah when I buy the other batteries. Check out my blog for more pics.

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I suspect you don't have that many Ah. By putting 2 x 6V batteries rated at 210 Ah in series you end up with 210 Ah at 12V. With 4 x 6V batteries of 210 Ah each you will get a 12v bank of 420 Ah, not 840 Ah.

> With 4 x 6V batteries of 210 Ah each you will get a 12v bank of 420 Ah, not 840 Ah.<

Even with 420AH a good question is how will they be recharged?

It becomes an even bigger hassle if 840AH are installed.

50% dead, About 15% to charge , with another 5% to push it in , would require an alt hot rated of about 175Amps per hour.With a very smart V reg.

Splitting into two banks to charge with two truck 135A Alts might work, with enough engine time.

With a charger from a noisemaker ($10.00 hour total run cost) it wont be fun!!

Well below is what Instate Battery sent me. You maybe correct. I will have have to email this guy back with a follow up question.

Charging isn't an issue. The batteries will be charge either by the engines or a on board battery charger.

Tom,
Thank you for your inquiry here at the home office of Interstate Batteries, Inc. The total ampere-hour would be 416Ah each bank with a grand total for 2 banks of 832Ah. I have attached a sheet for the recommended charging for your batteries. Always monitor the water levels and add distilled water when needed. The recommended water levels would be a minimum of ½” over the plates or 1/8” below the vent well (the tube looking down into each cell). Equalization should be done every 4-8 weeks or when specific gravities have a .010-.015 point difference between each individual cells. Fully charged the specific gravities should be 1.285 or greater. Let me know if you need any additional information.

Thanks,
Jeff Barron
Engineering & Technical Service Specialist
Interstate Batteries, Inc.
10200 Plano Rd. Suite #400
Dallas, Tx. 75238
Ph. 469-221-4655
Fax 469-374-6117
Email: jeff.barron@ibsa.com

http://www.topworkplaces.com/fronte...ny/desmoinesregister/interstate-all-battery-chttp://www.topworkplaces.com/frontend.php/national/standardhttp://www.facebook.com/interstatebatterieshttp://twitter.com/#!/interstatebatts

Here is the Charging recommendations they sent me:

Charging recommendations for 6-volt deep cycle batteries. GC2-XHD, GC2-HD, GC2-RD


Notes: 1. All charging voltages shown above are for 80 degrees F. For every 10 degrees above 80 F reduce voltage by 0.028 VPC. For every 10 degrees below 80 F increase the voltage by 0.028 VPC.
2. VPC = Voltage Per Cell
3. Charging current; C = The amp hour (Ah) capacity rated at the 20 hour rate.
4. Float condition is for long term storage / (several weeks) inactivity. 5. Equalize every 4 to 8 weeks or when the difference in specific gravity readings vary by 0.020 points or more and always after a normal charge.

Other Charging Notes/Tips/ Definitions: Temperature Compensation: Increase voltage by .028 volts per cell for every 10 degrees below 80 F. Decrease voltage by .028 volts per cell for every 10 degrees above 80F. Typical phases on multi-stage chargers: Bulk: Initial phase where the voltage builds and the most current is provided to the battery. This is typically where the maximum current that the charger is capable of providing is supplied to the battery. i.e. A 10 amp charger will provide at or near 10 amps during this phase. Absorption: The phase where the voltage set point is held constant. Current will decrease gradually during this point as the battery internal resistance comes up. Float:

The maintenance or finishing phase of the charging cycle. Voltage is set at a minimum during this phase (usually 13.0c-13.5v) and current drops significantly. The battery should be nearly complete by the time this phase is reached. An anti sulfation stage may be added where voltage spikes to high levels for very brief time periods for a set amount of time determined by the charger manufacturer, to convert the battery active material back to it's original state. Badly sulfated batteries will not usually respond to this charging regime and will need to be replaced.

Well so now it is all cleared up. See email below. It would appear that Ahs are only increased when you add batteries in parallel. So right now with 2 banks of 2 batteries each I have a total of 416Ahs. When I add the additional batteries, I will increase it to 832Ahs.

Thomas,

May I get a clarification with regard to what is being considered a bank of batteries just to insure I am on the same page.

2- golf car batteries connected in series for a total of 12-volts would only equal the ampere hour of the one battery. Example: Each battery is rated at 208 Ahs and when connected in series is equal to a total of 208 Ah for that bank.

So a four battery system in series/parallel is 416Ah.

To get to 1,664, it would take 16 six volt batteries connected in series/parallel.

Gale

From: Teseniar,Thomas A
Sent: Friday, December 05, 2014 9:47 AM
To: Mr Battery
Cc: Dawn Dumar (6839); Roy Hellmund (4654); Gale Kimbrough (4657)
Subject: RE: House Batteries for my Yacht

Good morning everyone.

I have a follow-up question regarding Ah.

Each battery bank currently has two batteries per bank, and each bank has 416Ah for a total of 832Ah for 2 banks according to your email below.

I have room to add 2 more batteries per bank for a total of 4 batteries per bank. I still have them connected in such a way that I have an output of 12Vdc from each bank. (series and parallel)

By added additional batteries does this increase the Ahs? By adding 2 additional batteries to each bank does that double the Ahs? (1664Ah)

Thanks again.

Thomas Teseniar