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Old 08-01-2024, 08:57   #61
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Join Date: Jul 2005
Location: Netherlands
Boat: Stern50
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Re: Two AGM in Parallel. One gets warm.

We have 4 of those Lifelines in a 24V 510Ah serial/parallel set up.
Because we do lots of long voyages, we cannot always get them cycled back to 100%.
We cycle normally between 60% and 90% by means of a DC generator.
That makes the batteries loose capacity over time.

So, when we are on shore power, and some capacity is lost, we perform such a conditioning charge. After a full 100% normal charge, put the units at 15,5 VDC (31V when on 24V) and let the current flow. Our Victron Multi+ makes, through VE-bus, these settings possible. Of course make sure no other equipment is connected at that time.

It helps.
Although the overall battery life is not any better, you can restore some loss of capacity this way and avoid premature throwing away these units.

Note: only Lifeline allows this procedure, don't do this with other brands.

Note: during the conditioning charge I keep track of temperature of the batteries. Just to be sure everything is OK.
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Old 08-01-2024, 09:06   #62
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Re: Two AGM in Parallel. One gets warm.

Yes. I have one of those ttesters. They are for starter batteries and not recommended for large AGMs. They can give some idea for large deep cycle batteries but to get more than a rough idea, the draw down tests are recommended, and that is what I did.

I am now wondering if they were fully charged and may repeat the test. In the meantime, they serve reasonably well but I am pricing replacements.

I will monitor that battery temperature difference, though, and disconnect one if indicated..
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Old 08-01-2024, 09:55   #63
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Re: Two AGM in Parallel. One gets warm.

Quote:
Originally Posted by s/v Jedi View Post
Come on guys, measure the current through each battery positive cable before deciding what to buy or even take apart!

You must diagnose and the clamp meter that we all carry (right?) is the tool.
Can be a.good start. If you have some load.
They are in parallel but if the connections are good and one is hotter than the other, at work at least it would be replaced. But might use a Thermal Imaging camera to see the cells from the side.

I am about to load test my batteries off of the boat. Will probably thermal image them as well.
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Old 08-01-2024, 10:21   #64
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Re: Two AGM in Parallel. One gets warm.

Quote:
Originally Posted by allendick View Post
OK. All good advice, Thanks.

I turned off the solar and shore chargers, and the house battery switch, then confirmed there was no draw from the pair,. I then measured a half amp flowing between the two at rest when disconnected from charging or load.

I would have expected it would take more than a half amp to generate that temperature difference, but the current should be zero, I assume. I assume also that it might change with time. Should I check over an hour or so?

As for disconnecting the batteries to see how they settle overnight, I live on this boat and have a DC fridge and lights. I suppose I could disconnect them one at a time, but would it be harmful to disconnect both and run the house on only the charger float? Seems chancey.

The other option is to disconnect them one at a time.
it is a mathematics problem.
can you run on one battery tonight? charger is working?
turn off everything and disconnect the two batteries from each other. Give them ten minutes to "rest" and then measure voltage individually.
Then if needed power in half hour, reconnect cooler battery.
wait even a couple hours and see if hot battery loses voltage dramatically?
I would suspect it levels about 12.0 volts fairly quickly.

Meanwhile, bad batteries work the charger excessively, example a warm shore cord (check the shore connectors for hot terminals and bad connections as this will stress them.

Last, an old battery will eventually show signs of boiling- expansion of case, and possible explosion when surged by , as emaple, starting the motor. makes a mess of the interior.
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Old 10-01-2024, 10:28   #65
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Re: Two AGM in Parallel. One gets warm.

I decided both AGM batteries are bad and am planning to order from here.

https://www.redodopower.com/

Comments?
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Old 10-01-2024, 11:40   #66
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Re: Two AGM in Parallel. One gets warm.

Redodo and LiTime are cheap. Will Price says LiTime are well built, but I don't know whether he has tested and torn apart a Redodo battery. I recently bought a 100 ahr LiTime, and it tested out at 105 ahr.

If you are wondering about choosing 100 ahr or 200 ahr models, be sure to check the rated amperage of the battery BMS. If the 200 ahr battery only has a 100 amp BMS, but 2 of the 100 ahr version. Be sure the BMS has cold weather protection.

A lot will depend on what the batteries will cost you in La Paz. Walmart sells Redodo online, and maybe you can pick them up at the La Paz store.
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Old 10-01-2024, 16:12   #67
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Re: Two AGM in Parallel. One gets warm.

I spent the day watching video and then went to 2 local dealers. One quoted me $4,440.20 USD for two Victron Lithium Battery LifePO4 12,8V/330Ah Smart batteries. Actually, I could get by with one.

However, the bargain batteries seem a better deal, but caveat emptor. I'll try to comile a report. Meantime a neighbour wants my old AGMs. His are worse.
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Old 10-01-2024, 16:30   #68
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Re: Two AGM in Parallel. One gets warm.

Quote:
Originally Posted by allendick View Post
I spent the day watching video and then went to 2 local dealers. One quoted me $4,440.20 USD for two Victron Lithium Battery LifePO4 12,8V/330Ah Smart batteries. Actually, I could get by with one.

However, the bargain batteries seem a better deal, but caveat emptor. I'll try to comile a report. Meantime a neighbour wants my old AGMs. His are worse.
Victron is IMHO seriously overpriced for their LFP batteries. There are a number of offerings between "bargain" and "overpriced" that are quite good and quite reasonable. Epoch has a 300Ah battery for $1199 that has Victron communications if you want to use the Victron ecosystem but skip the Victron Battery. There is an even cheaper version if you don't need Victron comms. Epoch seems to be the most recommended drop in by professionals.

https://www.epochbatteries.com/produ...och-essentials
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Old 10-01-2024, 16:37   #69
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Re: Two AGM in Parallel. One gets warm.

Thanks. My biggest problem has been finding the batteries these YouTubers tear apart and rate. Also this appears to be a fast-moving target and no matter what I see as the best deal today, I'll have buyers remorse tomorrow.
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Old 30-01-2024, 18:48   #70
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Re: Two AGM in Parallel. One gets warm.

Hi I have just set up two 300 ah HiXiMi LifeP04 batteries with smart BMS on my sailboat. They were the only ones I could get in Mexico at a decent price. Used Amazon.com.mx. No issues getting them delivered to the Marina in La Cruz but it did take 6 weeks.
So far so good. The cells seemed to be in really good balance and each battery was close to the other after charging. Feel free to contact me for more info.
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Old 30-01-2024, 19:01   #71
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Re: Two AGM in Parallel. One gets warm.

Thanks for the feedback. Very interesting.
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