Battery charging

We have wet cell lead acid batteries for the house bank and starting bank. We are in the process of installing a bow thruster and the recommendation is that a battery or battery bank be installed as close as possible to the unit. Thruster manufacturer recommends sealed AGM battery type.

My question will the two battery types be charged properly with the regulator set up for the lead acid battery banks or does the AGM require a different setting?
Fall back solution is to vent a lead acid battery to external vents as is done for industrial installations.

I would consider installing a separate battery charger in the vicinity of the new thruster AGMs, so the thruster system is entirely independent from your house bank.

Agm batts do indeed have a different charging profile then FLA batts. They also have a lower internal resistance so they can provide more current then a similar sized FLA. There are dc to dc battery chargers that can be programmed for different battery chemistries. Bonus is AGMs can be installed without specialized venting

Put a dedicated battery charger next to the battery and put the battery as close as you can get it to the thruster. This will keep the cables as short as possible. Connect the charger to a circuit fed by your inverter. This will ensure that the thruster battery is always fully charged and getting maximum voltage.

wwestman said:

Put a dedicated battery charger next to the battery and put the battery as close as you can get it to the thruster. This will keep the cables as short as possible. Connect the charger to a circuit fed by your inverter. This will ensure that the thruster battery is always fully charged and getting maximum voltage.

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This is what I did, and am extremely happy with the setup.

Ted

wwestman said:

Put a dedicated battery charger next to the battery and put the battery as close as you can get it to the thruster. This will keep the cables as short as possible. Connect the charger to a circuit fed by your inverter. This will ensure that the thruster battery is always fully charged and getting maximum voltage.

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I'm sure this is probably a common solution, but it's not one that I've heard before. That's brilliant and one more reason I read these threads even if the question doesn't really apply to any problem I'm trying to solve.

Thanks for that!

O C Diver said:

This is what I did, and am extremely happy with the setup.

Ted

Click to expand...

Bkay said:

I'm sure this is probably a common solution, but it's not one that I've heard before. That's brilliant and one more reason I read these threads even if the question doesn't really apply to any problem I'm trying to solve.

Thanks for that!

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Suggestions don't mention whether the separate charger is AC - DC or DC- DC.
I would think a DC-DC would have the advantage of keep the separate battys charged while cruising away from shore power. Otherwise thruster battys will remain down until you return to the dock.
Something to consider if you are starting from scratch.

Isn't that why the 2nd charger is wired to the inverter?

BDofMSP said:

Isn't that why the 2nd charger is wired to the inverter?

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Yes, that's my assumption.

The solution of using a small battery charger powered from the inverter or shore power when available makes a lot of sense. You can buy a good 5-10 amp charger for about $100, much cheaper than the Sterling DC to DC charger.


The only downside is that you have to keep the inverter on all of the time and it may not be very efficient at the low AC output required for the charger due to fixed DC requirements. Some inverters pull a couple of amps DC even when there is there is no AC load.


David

I originally had the small Prosport-6 charger (for top up of start batteries) on the Inverter side of the panel but my marine electrician did not like that and we put it on the “other side of the panel”. I think the possible cons are you are robbing “Peter to pay Paul” and I believe he thought that Inverter based charging an inefficient method and in some circumstances a possible danger to discharge the house bank. So I think you may want to get a bit more advice on this setup before you do so.

Jim

Well it certainly means you need to keep an eye on your house bank, but one should be doing that anyway. Am I missing something?

Normally the only time you would be using your thruster you would have your main(s) running, so the inverter bank would be getting fed by the alternator. Now if you decide to move the boat on the thruster alone that might impact your house battery.

BDofMSP said:

Isn't that why the 2nd charger is wired to the inverter?

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OK... agree I missed the recommendation to power it via the inverter. That would do it as well.