JonP wrote:

---

 I saw this the other day, which might help those trying to justify the switch to lithium or those kidding themselves lead is better www.altestore.com/blog/2020/11/replace-lead-acid-batteries-with-lithium-for-marine-and-rvs/

---

 When my almost 10 year old AGM's weighing in at 96kg (3 x 120Ah) reached the end of their useful life last year I was faced with the decision on whether to replace like for like or switch to lithiums. 

I had, & still have no doubt that lithium have many benefits which AGM's don't. 

However my decision came down to a cost/benefit analysis.  Bottom line was that my AGM's had lasted for 9 years & 10 months & had done all I needed them to do. We have no need for high discharge rates, & no room to fit any extra appliances which would require high discharge rates. I didn't need faster charging as the system with the AGM's would see the batteries back to float by midday on most days, & the system had seen us quite capable of indefinite self sufficiency power wise. In five year full time travel we had never needed to plug into mains power or to use a generator. 

The only thing which lithium offered us that was desirable to me was a significant weight saving. 

So when I could replace my 3x 120Ah Ritar AGMs, with no other changes needed to my charging system for less than the cost of a single quality 120Ah Lithium battery I had to ask myself how much the weight saving was worth.

Realistically replacing the 3x 120Ah AGM's for a 200Ah lithium would have been a reasonable 'exchange' in terms of useable capacity & would save around 70kg.

The cost of a reasonable quality 200ah lithium which I might hopefully get another 10 years of use from was around 3 times the cost (in round figures) of the cost of the AGM's. In Addition was the cost for a different dc to dc charger. Overall Lithium +charger was going to cost me approx $2500 more than staying with AGM's.  That was not only a very expensive bit of weight saving, but also some considerable inconvenience/extra work to swap out the dc to dc charger (particularly as we were 'on the road' without access to my workshop back home any time soon). The non lithium spec Redarc BCDC1240 will not fully charge lithium batteries - regardless of what any battery sellers might say about their BMS. It was also a lot of extra money to simply keep on doing what I could already do. 

In the end, whilst the weight saving was certainly attractive, I had to accept that we had managed just fine with that weight for years & thus the cost of the weight savings could not be justified, so I replaced the old Ritar AGM's with new Ritar AGM's. 

I don't suggest that what made most sense for me would apply to many others, but I do suggest that unless anyone is actually able to make use of the significant benefits that lithium batteries offer over lead acid's then perhaps they are not worth buying. 

If/when we change our travel rig to something a bit more luxurious, where the higher discharge rates of of lithiums would be utilised then using lithiums would be a no brainer. 

Hitting the road wrote:

---

Cheers Mike...I hear you. My reasoning is; I did have a situation not long ago where I had the BMPRO BMS shut down the power supply due to low voltage. Not real convenient as it was about 7pm and still needed power to run the water pump for showers as well as some lights.

Given the BMS shuts the power off when it senses the batteries at 11.8v I think, this can easily happen if there is a sudden draw on the batteries for some reason sensed by the BMS and it shuts power down to "protect' the battery.

Totally my fault in this case, camping at an off grid site later in the day after picking the van up, I didn't put the panels out and used lights, water pump, radio and TV, couple of phones charging etc that night...also left the gas water heater on. (It actually uses a small amount of 12v power constantly...likely to keep the gas solenoid open while lit, I wasn't aware of that at the time.) Next day didn't put the panels out as the weather was crappy and overcast, thinking I'll be fine without. So then after 40 odd hours off grid, bingo, no power, shut down by the BMS. After isolating the batteries for half an hour or so they recovered enough to run the water pump and some lights.

Panels went out next day and all was good...I am also a lot more savvy now with power usage!

It was a wake up call really...certainly got a far better grip on the electrical setup in the van. The issue that time sheets back to keeping my van in storage as I have no room at home to keep it. It had sat for maybe 8 weeks without any 240v power on to charge the batteries, so hit the road with maybe 70% battery level I reckon, (showed 12.6v on the panel),  I likely had in reality probably less than 80 amps usable before the BMS stepped in...batteries did not charge while traveling. (it lives in a huge shed with other vans and boats so no solar input either.)

Now when I pick the van up I really need to book in to a Park for a couple of days straight up to top the batteries up or potentially run in to the same problem again. This is why I am opting to go Lithium...(and will eventually fit an Inverter), putting in 350 amps will give me over double what I have now in usable capacity available...and given the travel I am going to do I could easily be off grid for a few days at a time...that coupled with the now unreliable electricity supplies in this country there is never a guarantee where you stop will have 240v power available. As you note dropping the batteries below 50% occasionally won't kill them, but the BMS isn't programmable as far as I can see to alter the shut down voltage. I could get rid of the existing BMS but that means fitting a new power distribution set up as well...getting beyond what I wish to do.

Thanks mate for the tip on the charger as well...much appreciated.

---

For the last week I have been trying to sort out a problem with the 12v power supply on our 6 mth old van. We had fitted a caravan cover about 5 weeks ago and when we removed it we had no 12V power. First thought was no problem the solar panels hadnt been producing power so the batteries would just need recharging. A couple of days in the sun, then hooked to mains power, then to the car (it has DC2DC charger) all had no affect. I saw that there were no indicator lights or readings illuminating on the charger panel regardless of power input. All the 240v appliances were working with the mains connected except for the fridge which had nothing showing on the control panel.. The van was built with the Projector PM30 battery management system, 2 x 100Ah Lithium batteries, 2 x 200w solar panels, 3000w inverter and a DC2DC charger. I went back to the dealer who rang the manufactuer who then directed us to the battery supplier for advice on how to bring the batteries back up. According to the battery supplier if there had been a very low discharge ie. a reading light left on and the 12v load not been switched off the system may not have picked up the slow discharge and the protection would not have shut down the batteries. This would result in draining them to a point where the charger wasn't seeing them. Even worse news for me was that if the batteries had been damaged they would not be covered under warranty as it would be classified as misuse. Their advice was to take a voltage reading on each battery (10.8v & 11v) remove them and place them on an external charger before reinstalling them then the charger should then be able to reboot. Luckily that excercise proved successful and we are now back in buisness including the fridge which was not working because the control panel is 12v. I believe after opening the tunnel boot and seeing that the light had been left on that I had probably forgotten to turn off the 12v system prior to putting the cover on. Now I will double check that I have shut it down prior to storage because if I would like to try and avoid the risk/cost of having to replace damaged Lithium batteries.

BB

-- Edited by The Belmont Bear on Sunday 5th of March 2023 11:14:50 AM