Re: [electricboats] AGM or LiFePo4

I still use flooded lead acid --- on a 1920 Milburn electric car I own.
Its Interstate golf cart (T105 style) batteries are pushing 9 years now (time flies). Last year I wanted to drive the ol' car to work (16mi one way) and back. But I didn't have much confidence in the batteries. Over a weekend, I charged the batteries, first with golf-cart 25amp chargers (one 48v, the other 36v---pack is 84v) but the charging stopped without too many amp-hours put in. So I switched to my nom. 106v current-limited power supply, which didn't add a whole lot either. Checking the cells, I found that the electrolyte levels weren't very good at all. What could I do? Well, get my 50amp current limited 12v charger and put it across each 6v battery, that's what! Actually, that charger had recently had something go out on it so it was not voltage-limiting at 14-15v and was instead putting out maybe 20v. So after rebuilding the charger's cables to handle the 50amps, I turned on this charger and clipped it across each pair or triplet of series batteries, pumping high current into them until I just started to smell outgassing, or the "burping" in the cells was getting too lively or contacts getting warm or the volts per cell changes suggested it's time to disconnect. I repeated for each of the 7 pairs of batteries. The result: After doing this, driving the car around, then repeating this treatment, the electrolyte levels of every cell returned to the GOOD range. And the ordinary golf cart chargers then did their job better after. Ultimately, there was plenty of juice to get me to the car show at work, where the car one Best In Show :-). I drove it to work another day or two later also.

Bottom line: Don't ignore the risks of sulfation of PbA batteries that are not cycled with any regularity. And to recover these, you need to do more than put a standard charger on them since the voltage-limitation will not allow the clearing of the sulfation. Some badly sulfated batteries appear completely dead unless hit with 50-150vDC (current limited of course) to get the current to start flowing. And even then, if you monitor the voltage, you'll find that the voltage actually "drops" as the battery charges.
Be very mindful of temperature and outgassing, particularly if you are trying to bring capacity back to a sealed- or AGM battery. Any sulfur released is not coming back---and you need that sulfuric acid.

-MT

-----Original Message-----
From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Matthew Geier
Sent: Monday, April 27, 2020 1:47 PM
To: electricboats@groups.io
Subject: Re: [electricboats] AGM or LiFePo4


On 28/4/20 12:43 am, greenpjs04 wrote:
> . The Torqeedo would shut down due to "depleted batteries", but I was always able to turn it off and then back on where upon I could return home at a slower pace.
>
> Anyway, I suppose it is time to replace the batteries. I can't complain about getting 10 years out of them. As I see it, I have two options:
>
I'm in the same position, after 10 years my Trojan flooded T145s are showing 'voltage depression' rather rapidly. They will have to be replaced before next season.

I'm sort of in the sane position, replace the Trojans with the same or switch to one of the modern Li chemistries.








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