#44424  by Justintime
 Tue Oct 30, 2012 8:29 pm
Chris, I have been reading your posts with interest, because we have a very similar situation to you (caravan, coffee machine, 1800 watt inverter, microwave, 200 amp hr AGM's, 280 watt solar) and replaced our batteries in June after 18 months use (totally fortunate the supplier decided they should have coped and replaced under warranty). I researched the lithium option because weight was also a big issue. I wasn't a forum member then but separately came to pretty much the same conclusions as you, although decided to wait and see how it developed as time was on my side with the new batteries. Summer has never been a problem, only winter. I am reluctantly looking at a generator, which I won't be able to use in many places I go to, but ultimately I see lithium batteries as the future. So please keep the posts going, your experience in the next year will give a great insight.
 #46758  by Nut17
 Sat Dec 15, 2012 9:52 pm
Hi Justintime, one quite important thing that could be the cause of an early demise of your 200 amp /hr AGM battery bank is the excessive load put on them when operating the coffee machine. With the monitor we have now I regularly witness up 125 amps being drawn from the battery while the coffee is being brewed. This high drain is only for a max of about 1.5 minutes and has no detrimental effect on the Lithium battery, but research has led me to believe that even for a short duration, AGM batteries cannot tolerate that high current drain. On an American forum they were recommending C5 which equates to one fifth of the batteries capacity, which would allow only a current draw of 40 Amps from a 200 Amp Hr AGM battery bank.

Cheers Chris
 #46774  by Justintime
 Sun Dec 16, 2012 10:38 am
Thanks Chris, I know where you are coming from and I told the battery retailer (Battery Warehouse in Tauranga) that I was concerned by that. But they still advised that there should be no problem with that for those batteries, and they replaced them free of charge. Only one was really bad, but the other had dropped down as well, presumably taking up the slack for the bad one. Our coffee machine doesn't take more than 60 amps, but we have occasionally used the microwave and that goes up to about 93 amps, so I have dropped that. My thoughts are that if I blow these ones up, then lithium it is, so am still assuming that yours are in good shape? Cheers, Dene
 #46778  by Nut17
 Sun Dec 16, 2012 1:10 pm
Hi Dene, the battery is still functioning as intended, which in my case exceeds all my expectations. Our good friends who live nearby and often travel with us with their van have invested in a Votronic battery monitor for their AGM battery and are now happy that they know accurately, the state of charge as well as current in and out. Would definitely recommend that you invest in a monitor, as you will need one when you move to lithium batteries.

Cheers Chris
 #46790  by Justintime
 Sun Dec 16, 2012 6:00 pm
Hi Chris, We have a Redarc Battery Management system which is a fairly advanced battery monitor come management system, so all good there. Like a lot of charging systems though it has various options for charging batteries, and lithium isn't one of them. I doubt also whether your charging system has that option (may be wrong but I don't yet know of any that do), so what battery charging option (e.g AGM, Gel, Flooded) did AA Solar tell you to use so that they would honour the warranty. Thanks, Dene
 #46793  by Nut17
 Sun Dec 16, 2012 7:12 pm
With a nominal static voltage of 13.2v for the lithium pack, standard chargers tend to be on the low side voltage wise to do a proper job. The bulk charging should be done at 14.6v and the float should be 13.6v. Flooded wet settings will be as close as you can get to these figures unless your charger has adjustable ouputs. My solar controller has fully adjustable outputs so that has been adjusted to suit. To the best of my knowledge the C-Tek M300 mains charger is running the standard wet flooded setting as set up by the guys at AA Solar.

Cheers Chris
 #46803  by Justintime
 Sun Dec 16, 2012 10:12 pm
The Redarc BMS runs a bulk charge at 14.8 volts and float at 13.5 volts on the flooded setting, so looks like that would do it. Because its an integrated system, that will cover all the AC, solar or DC charging. Looks like a viable option. But need to blow up the current batteries first. So heaps of coffee and microwaved meals these holidays. Thanks for that. Cheers, Dene
 #47200  by John&Helen
 Sun Dec 23, 2012 6:56 am
Hi Chris.

After living for three weeks in the 5th Wheeler, one thing I sort of appreciated was ascertaining the 12V 100A/hr battery SOC by looking at the (full time ON) Voltmeter. It never got below 12.4V overnight, its that reading that I used to guesstimate the previous days useage, the main load being the 60W LED TV. The TV dropped the battery voltage 0.5V whenever it was switched on.

It occurred to me, that with your LiFe battery setup, unless you had a fancy Battery SOC meter, youd always be wondering how much life remained in the battery. LiFe batteries maintain a high voltage almost irrespective of load, so my simple morning glance at the voltmeter wouldnt work so well?
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