Re: Lithium Battery

by Peter Brown Tue Nov 02, 2021 7:47 pm

If the Lithium battery is allowed to take the charge current that it is capable of accepting then the maximum size battery that the standard Sargent/AS system can service is 60Ah and from what I read on this forum they are having to increase the fuse in the charge circuit from 20A to 25A with the 60Ah battery.

The lithium batteries include battery management circuitry that in most cases can be adjusted to control the charging current, I can only assume that the installers are doing this to allow Lithium batteries of a total of over 60Ah to be installed. If this is the case they are considerably increasing the time it will take to charge the battery(ies) and negating one of the three potential benefits of Lithium over Lead Acid. The user will still benefit from the lighter weight and greater depth of discharge but if they so use the extra capacity will have to wait for several hours of charge to replenish it so economically would have been better reverting to Lead Acid or staying at 60Ah Lithium - that will give the performance of an 110AH Lead Acid.

All of this will be totally transparent when on EHU but after three or four days off grid whether using the engine or mains charger expect it to take 8 to 10 hours to recharge.

by Kevinktwo Wed Nov 03, 2021 3:00 pm

[You must be registered and logged in to see this link.] Hi Stuart, I bought a second 100amp lithium and still pondering how to connect it to the Sargent setup, how was it fitted so as not to overload the present infrastructure when charging...

by StuartB Wed Nov 03, 2021 3:42 pm

To be honest I don't know the details, I got Conrad Anderson in Birmingham to do it for me. If it would be any help I could take some photos(its very tight in there though) of the set up if that would be any help to you. It does through the Sargent system somehow.

by Kevinktwo Fri Nov 05, 2021 1:16 pm

Hi Stuart - That would be brilliant, would much appreciate it. Kind Regards Kevin.

by Peter Brown Fri Nov 05, 2021 3:12 pm

The lithium batteries in my garden tools wouldn't charge this morning as it was too cold in the shed - I had to warm them up in the house before I could charge them.

This made me wonder. We are used to a solar installation keeping batteries in good condition during long periods of winter storage but its possible that a long cold snap with bright sunlight days may damage cheaper Lithium batteries that don't disable charging in cold temperatures.

by BornAgain Fri Nov 05, 2021 9:09 pm

What’s not to like about Lithium batteries? Smaller, lighter and greater longevity. Me and my fellow golfers would never go back to a lead acid battery golf trolley! It’s one of the major reasons that EVs are now replacing combustion engine cars (that and UJTs). However, just like lead acid, they require their own charging regime and it’s true of all lithium batteries whether they are in your smart phone or an EV that if you charge to 100% every time the life will be reduced. Cars have very sophisticated battery management systems (BMS) that prevent charging to 100% and fully discharging.

What I am not clear about is how the Sargent BMS works to maintain the life of a lithium battery but if it works correctly most of us will never need to replace the leisure battery which is more than can be said for lead acid.

by Kevinktwo Sat Nov 06, 2021 10:01 am

Born Again, the other thing to take into account is the BMS built into the Lithium Battery, unfortunately, the Li Batteries Autosleeper are using are not particularly sophisticated, and for instance, I can find no cut off to prevent the Battery from charging at low temperature and the dealers I have spoken to have all said that they had not been told that lithium batteries should not be charged at low temps (even though it states this on the battery data sheet.

by BornAgain Sat Nov 06, 2021 8:13 pm

Kevinktwo wrote:Born Again, the other thing to take into account is the BMS built into the Lithium Battery, unfortunately, the Li Batteries Autosleeper are using are not particularly sophisticated, and for instance, I can find no cut off to prevent the Battery from charging at low temperature and the dealers I have spoken to have all said that they had not been told that lithium batteries should not be charged at low temps (even though it states this on the battery data sheet.

I dismantled and repaired a lithium battery pack and, as you say, they have a control module but also the charging regime is different so you cannot replace a lead acid directly with lithium. A good BMS prevents low temperature charging and limits the charging range. Having said that, our experience with lithium batteries even with basic chargers is that you get a substantially longer life plus, of course, the size and weight advantage. They are the future but come at quite an additional cost.

by aldhp21 Mon Nov 08, 2021 3:14 pm

We have a 2017 Broadway FB and because our two lead acid batteries were not holding power when off grid we opted to go with Lithium.

We had a 120amp Lithium fitted but also needed a Victron shunt, a Victron solar regulator and a B2B. We were warned at the time that the Sargent charger we had was ok but we would be better off changing the charger. (Sargent charger wants to go into float mode at 13.6v and Lithium want to be charged up to 14.2 - I may have the numbers slightly wrong but they're in that ball park). In order to get the charger to top the battery up to the 14.2 it was suggested to switch something on that had a draw bigger than 2amps and it would force the Sargent to fully top it up.

So the van sat outside on mains for the last 10 days and I've been able to monitor what's going on as the Victron units (shunt and solar reg) can feed Bluetooth apps and you can see what's going on.

What transpired is the battery not being charged up as expected. It should have gone into float mode but it appeared it was turning itself off and then the battery started to drain. This may well explain the problem with my old batteries.

So I phoned Sargent and explained the issue. They informed me that they had some faulty chargers from around 2017 but these were extremely rare and they'd only found a few. But it would explain some of the characteristics that I was seeing. They would supply me with a replacement charger for the cost of £150 (now out of warranty!!), but....... "I would be better off replacing with another manufacturers charger, as the Sargent ones aren't good enough for lithium.

My charger is being replaced with a Victron one so I'll update after then. I intend to follow up with Sargent in the next few weeks. If they knew of the fault should that not have been a recall?

by LewAnn Wed Nov 10, 2021 12:05 pm

I upgraded to the 84Ah Lithium battery rather than the default 60Ah. First couple of trips, Fuses blown, so replaced 20A fuses in battery circuit with 25A on advice of dealer. On return from a trip about 4 weeks ago, battery went to zero after about a week. I was pretty certain that everything was switched off. Dealer advised charge and see what happens. Two weeks ago put van away for the winter with fully charged battery, and double checked everything switched off. Battery steady at 13.3V for about 10 days. Now dipping, reached 11.8V today, expecting call from Sargent soon to say Leisure Battery flat. Anyone else experienced this?