Brainstorming last night....
I dusted off an upgrade I was planning for the '91 U300, maybe in the next Foretravel...
The plan was to retain the existing 12 volt chassis and house systems for 12 volt lighting, fans, and water pump, etc, and add a 48 volt battery system. Going to 48 volts lowers the inverter current by a factor of 4 which greatly reduces the size of the wiring.
I wanted to make the coach all-electric and convert the entire coach including both A/Cs to power supplied by a 240 volt split phase inverter. Also, beef up the alternator to provide high current charging and running 1 A/C while driving. This change does eliminate being able to use a 30 amp 120 volt pedestal.
I could then install a 240v induction cooktop, 240v dryer, 240v in-floor and baseboard heat, and remove the propane tank to make room for the new 48v battery bank.
After considering lithium, with the cost and temperature limitations I decided to go AGM (although some have developed solutions for the lithium temperature control and cost continues to come down).
I didn't show solar in the plan but of course that could be a future improvement.
(I'm pretty sure this project would void the warranty)
Parts list
- 48v - 4X 12v 245 AH AGM - approx 12 kWh - 6 kWh at 50% discharge
https://www.oreillyauto.com/detail/c/fleet-heavy-duty/super-start-fleet-heavy-duty-battery-group-size-8d/ssbl/agm8dt904
- 48v - 8X 6v 335 AH AGM - approx 16 kWh - 8 kWh at 50% discharge
DC335-6 | Fullriver Battery (https://www.fullriverbattery.com/product/dc335-6/)
- Delco 55si 430 amp J180 mount alternator
61003345 by DELCO REMY - 55SI New Alternator (https://www.finditparts.com/products/8710911/delco-remy-61003345)
- AIMS 12v-240v 4000 watt inverter
4000 Watt 12 Volt Pure Sine Inverter Charger 120/240 (https://www.aimscorp.net/4000-Watt-12-Volt-Pure-Sine-Inverter-Charger-120-240.html)
- AIMS 48v-240v 10000 watt inverter w/ 50 amp transfer switch
10000-Watt Pure Sine Inverter Charger (https://www.aimscorp.net/10000-Watt-Inverter-Charger-48-volt-to-120-240vac.html)
- Blue Sea 500 amp 12v signal relay with auto release
ML-RBS Remote Battery Switch with Manual Control Auto-Release - 12V - Blue... (https://www.bluesea.com/products/7713/ML-RBS_Remote_Battery_Switch_with_Manual_Control_Auto-Release_-_12V)
(http://www.foreforums.com/MGalleryItem.php?id=4813)
48v is a great idea, IMHO AGM isn't.
I have been doing a ton of research on how to set up my 99 U320 for full time duty post retirement in about a year. My goal is to have enough battery and solar to be able to run both AC units, as well as the other loads, off grid during the day, and one AC overnight. Using the space from taking the propane tank out, and utilizing the current house battery location I am pretty sure I can get there. I am assuming some very efficient AC units as well.
Hot and cold can be an issue for LifeP04 batteries, but it is easy to resolve with a good BMS, a thermostat, a fan and a heating pad.
Cost is very close per usable amp hr. If you are willing to build you own batteries the cost is less.
Charge and discharge rates are much higher.
Charge cycle counts are way better on the LifeP04 batteries.
Apples to apples I would use the 5 hour AH rate, not the 20 hour to compare capacity, if you want to run any large loads.
The LifeP04 batteries are about 1/3 the weight vs AGM per usable AH. 8 of those 6 volts are 372.8 Kg or about 820 lbs. Similar usable capacity LifeP04 batteries would weigh about 125kg or about 275 lbs.
This guy (https://www.youtube.com/user/errolprowse) does a lot of battery and solar testing and good videos on YouTube. A nerd for sure but a lot of good information. His web site Mobile Solar Power Made Easy! - Mobile Solar Power: Made Easy! DIY Off-grid... (https://www.mobile-solarpower.com/) is also a really good source.
Sounds complicated. I just sold a Prevost with 12, 24, and 120 volt systems.
Yes, I think once you have an AGM battery bank for the 12V House, then a separate Lithium 48V bank for the 110V distribution in the bus is the way to go. But, unfortunately, the pricing on Lithium with built in BMS at this time, July 2021, is twice that of a good quality AGM. So, for now, I think Firefly OASIS Group 31 AGMs is a better bang for the buck, at least for me.
As some of you know, I'm also investigating a 48V system for the 110V part of the house. I'm taking a slightly different approach.
1 - I have already purchased 8 of the Firefly OASIS Group 31 AGM batteries to put into the battery compartment where the bus had 3 8D Gel House batteries. Those used to be charged by a Xantrex Prosine 2.5. The Xantrex is coming out. In its place, a Victron Multiplus II 12/3000/120-50 2x 120V will be installed. That setup will be a 928 AH 12V battery bank dedicated exclusively to the 12V distribution of the bus. I don't plan to take the OASIS batteries below 30% SOC.
Note: But, for now, I will be using those batteries temporarily, along with the Multiplus for both 12V and 110V for the bus.
2 - In the future, I plan a separate battery bank for the 110V. That will be managed by a Quattro 48/10000/140-100/100 120V. That bank would ideally be 4 of the Battleborn BBGC3 in series for a total 270 AH at 48V. The reason for the BBGC3 is because of their convenient form factor. Four of those and the Quattro will fit nicely and take less than 2' in the back of one of the compartments in the bus. The relative low weight of lithiums per AH compared to Lead Acid is also nice. I don't plan to take the Lithiums below 20% SOC.
Update (7/1/2021): So, all of the above with the BBGC3 would be ideal, but price is a constraint. So, the Firefly OASIS will be used for the 48V and 12V banks.
- My plans are to keep the Propane/Electric refrigerator and propane stove. I already have Aquahot for heating.
- Since propane will satisfactorily take care of refrigeration and cooking and the Aquahot takes care of heating, the 110V battery bank will easily take care of supporting 1 of the 15000 BTU AC while driving.
- The 140 amps of charging from the Quattro will work great with the 270 AH lithiums. That is because the 10 KW generator could bulk charge those batteries in less than 1.5 hours or so. Then solar could absorption charge for the rest of the day.
Note: But, because the BBGC3 are not currently in the budget ($2900 ea.), I shall wait for a sale on those to start on that project. If the OASIS were available in the form factor of the BBGC3, I could have used those instead. May be Battleborn would like to sponsor this project. :D
Update (7/1/2021): I will use the Firefly OASIS for both banks.
3 - With the 1 Quattro in the bus and the Lithiums, I will then add another 48V battery bank at the homestead and another 48V Quattro and set them up in a split setup for home power backup. But, that is another future project.
4 - I also like Peter's idea of upgrading the alternator to 430 amp. That's another future project. I will trigger that project if I ever decide to buy a Hybrid or electric toad. In that case, I could have one or more BBGC3 installed in a box next to the Chassis batteries by the engine. Another appropriate inverter could sit back there. I could then pump alternator sourced juice into the electric toad while traveling to some destination. Alternatively, I could have the inverter in the back of the bus keeping the Multiplus and Quattro at the front of the bus charging the House banks, both 12V and 110V, by pumping 110V to them, at the loss of efficiency.
5 - Future solar for all battery banks.
The above setup would work great to provide AC while driving, while boondocking and also for charging an electric toad. I just need to keep reworking the budget!
We should talk. I might have a coach that's 3/4+ there.
Just curious - if I'm calculating this right - 48 volts x 140 amps = 6720 watts. At 120 volts this is 56 amps. Most 120 volt circuits (that I know of) only support at most 30 amps. Don't see where 56 amps will come from...
On shore power, 50 amps 240V split circuit, 2x 120 into the Quattro. From the Powertech 10 KW generator. Even with the 120V single output from the generator you could get the amps you need.
I think this is the generator that I have. I'll have to check.
https://cdn.shopify.com/s/files/1/0062/4072/files/PT10000.pdf?10436588421054156463
Wow, that generator can put out a healthy 120 volts at 82 amps. So, I'm thinking on a 50 amp pedestal you're fine, when on a 30 amp pedestal the Quattro will need to limit current draw.
Or, avoid 30 amp pedestals which was my plan with my design. We have always preferred boondocking and rarely plug in.
In my '91 U300 the Onan 7.5 kw generator put out 240 V across both legs (I verified this) so this is why I planned to go with a 240 V split phase inverter.
Unfortunately later year coaches seem to have gone to generators wired for 120 V, not sure why you would take a high end 50 amp 240 V capable coach and then put in a 8 kw or 10 kw generator and wire it for 120 V...? Maybe cost of the additional regulation needed to balance loads between legs in the power panel.
The old Onans had an integrated autotransformer with a center tap that balanced the load on the generator. Victron sells a couple of autotransformers for split phase power applications.
Aims 240 V inverters use an internal autotransformer to provide split phase power from either the inverter or 240 V single phase input. That's why the 12 kw weighs 174 lbs. This solves the load balancing issues you have with 2 stacked inverters and/or a 120 V generator converted to 240 V.
Ernie, not disagreeing with you at all, it is complicated.
To me, a 48V upgrade like I still plan to do some day, addresses shortcomings (IMO) in the electrical system of most coaches - not just Foretravels - like undersized battery bank, undersized alternator, undersized inverter powering only part of the coach, 120V generator (on most later model coaches) and no charging of engine battery on shore power.
These are all cost related tradeoffs, manufacturers design coaches for a price point to make a profit.
With these upgrades the electrical system can fully utilize the awesome 50 amp 240V wiring the coach was designed with, 240V upgrades are possible, and A/C can be used when driving or boondocking without the generator.
I enjoy modifying and updating with new and improved options that are available today. If most coach owners are happy with the electrical system as originally designed, great!! Nothing wrong with that.
We are pleased with ours. Our Liberty and previous Wanderlodge, all had 300 amp alternators, which could power the city block. And with that comes all the confusion, on my part, how that works. At 73+ years on the planet, shifting to simple is our plan.