Recovering a sealed lead acid battery - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

ScottBouch · 25th Jul 2025, 11:13 pm

So after taking your collective advice, today I received a 12.8 V 50 Ah lifepo4 from Eco Worthy.

I connnected it to our tent solar PV array, and had it charging merrily at 7A in decent afternoon sunshine!

It is a very nice battery, double the capacity and half the weight of the previous sealed lead acid. It states that it can take a continuous charge and discharge of up to 50 A! Mental!

I will test it over the weekend, running our camping fridge that I recently rebuilt using Peltier heat pumps, I gave this a variable current control, so can fiddle about, but may automate this load against sun intensity and battery charge.. a diode least gate may be of use here.

Cheers, Scott

ScottBouch · 26th Jul 2025, 7:30 am

PS, this battery includes its own internal BMS in the casing to manage the cells internally. Shame the top is glued/bonded on as I'd have liked to see inside!

it comes with a nice little carry handle too fitted in the top, which may seem an odd feature to emphasise, but when you have to reach deep into the camping trailer to fetch it out, little things like this do help!

locknut · 26th Jul 2025, 10:29 am

Quote:

Originally Posted by cmjones01

Whilst working on something else, I've just discovered that apparently the very popular DeWalt Lithium power tool batteries don't actually do any charge balancing during charging, though the batteries do have connections for it, the charger doesn't use them. They do however monitor individual cell voltages to shut off the battery charger if any one of them goes too high. So even the 'big boys' don't necessarily use a proper BMS.

DeWalt batteries don't protect the cells from overdischarge either - cheap third party work lamps (and other accessories), if left connected for long periods, can kill the batteries.

kalee20 · 26th Jul 2025, 10:59 am

I've generally had good results from sealed lead-acid batteries. Though they do have their limitations...

Overcharging leads to gassing, possible venting of the seals, and permanent loss of electrolyte. So, charge voltage needs to be carefully controlled, and compensated for the ambient temperature (memory says 2.5mV per °C per cell, so that's a change of float voltage of 300mV for a 12V battery for a temperature range of 5 - 25°C. It's not negligible).

A second degradation mechanism is leaving discharged. As the lead-acid cell discharges, the active material on both plates turns to lead sulphate. But left thus, the fine-structure of the sulphate slowly crystallises. Because lead sulphate is a poor conductor of electricity, it is very difficult to return to the lead, and lead peroxide, of a charged cell.

So, as soon as possible on discharge, put back on charge. And if you can't, then keep the battery cold - low temperatures slow down the crystallisation process.

Recovery from loss of electrolyte is only possible if you can add more. Recovery from sulphation is possible to an extent, by slow charging from a high voltage until the battery is accepting a charge, and then several charge / discharge cycles.

25th Jul 2025, 11:13 pm	#21
ScottBouch Octode Join Date: Feb 2013 Location: Leicestershire, UK. Posts: 1,572	Re: Recovering a sealed lead acid battery So after taking your collective advice, today I received a 12.8 V 50 Ah lifepo4 from Eco Worthy. I connnected it to our tent solar PV array, and had it charging merrily at 7A in decent afternoon sunshine! It is a very nice battery, double the capacity and half the weight of the previous sealed lead acid. It states that it can take a continuous charge and discharge of up to 50 A! Mental! I will test it over the weekend, running our camping fridge that I recently rebuilt using Peltier heat pumps, I gave this a variable current control, so can fiddle about, but may automate this load against sun intensity and battery charge.. a diode least gate may be of use here. Cheers, Scott __________________ www.scottbouch.com

26th Jul 2025, 7:30 am	#22
ScottBouch Octode Join Date: Feb 2013 Location: Leicestershire, UK. Posts: 1,572	Re: Recovering a sealed lead acid battery PS, this battery includes its own internal BMS in the casing to manage the cells internally. Shame the top is glued/bonded on as I'd have liked to see inside! it comes with a nice little carry handle too fitted in the top, which may seem an odd feature to emphasise, but when you have to reach deep into the camping trailer to fetch it out, little things like this do help! __________________ www.scottbouch.com

26th Jul 2025, 10:59 am	#24
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,835	Re: Recovering a sealed lead acid battery I've generally had good results from sealed lead-acid batteries. Though they do have their limitations... Overcharging leads to gassing, possible venting of the seals, and permanent loss of electrolyte. So, charge voltage needs to be carefully controlled, and compensated for the ambient temperature (memory says 2.5mV per °C per cell, so that's a change of float voltage of 300mV for a 12V battery for a temperature range of 5 - 25°C. It's not negligible). A second degradation mechanism is leaving discharged. As the lead-acid cell discharges, the active material on both plates turns to lead sulphate. But left thus, the fine-structure of the sulphate slowly crystallises. Because lead sulphate is a poor conductor of electricity, it is very difficult to return to the lead, and lead peroxide, of a charged cell. So, as soon as possible on discharge, put back on charge. And if you can't, then keep the battery cold - low temperatures slow down the crystallisation process. Recovery from loss of electrolyte is only possible if you can add more. Recovery from sulphation is possible to an extent, by slow charging from a high voltage until the battery is accepting a charge, and then several charge / discharge cycles.