24 volt battery bank?

pianotuna wrote:
Hi,

With sufficient solar who cares about efficiency?

The pure twelve volt loads amount to about 40 amp-hours a day so the losses would amount to 8 amp-hours. So again, who cares about efficiency?

hbski wrote:

pianotuna wrote:
You already have a converter. Run that from an inverter or shore power for the 12 volt needs.

90ish % inverter efficiency, times typical 80% converter efficiency probably prohibits this....but good for back up.

but DC to DC can be >95% efficient (per manufacturer anyway)

but for $90 for a Victron 25A 24 to 12V @ 96% why not?

it would replace the converter 80% X the 93.7% peak efficiency total of ~75% PLUS extra transmission losses going from 24V DC to 120V AC to 12V DC. Not to mention peak efficiency is only at a specific output (~1400W on the 4024) and typical efficiency will likely be 90% (or less) garnering 72% or less.

Plus some of us have limited roof space for solar!

Hi,

With sufficient solar who cares about efficiency?

The pure twelve volt loads amount to about 40 amp-hours a day so the losses would amount to 8 amp-hours. So again, who cares about efficiency?

hbski wrote:

pianotuna wrote:
You already have a converter. Run that from an inverter or shore power for the 12 volt needs.

90ish % inverter efficiency, times typical 80% converter efficiency probably prohibits this....but good for back up.

but DC to DC can be >95% efficient (per manufacturer anyway)

pianotuna wrote:
You already have a converter. Run that from an inverter or shore power for the 12 volt needs.

90ish % inverter efficiency, times typical 80% converter efficiency probably prohibits this....but good for back up.

but DC to DC can be >95% efficient (per manufacturer anyway)

MEXICOWANDERER wrote:
Problem is with the cost of an extremely dependable DC Bucker. My bus is 24 volt and I have zero appliances that require electricity. What folks here seem to not touched on is when you are cruising down Route 66, what battery recharging system will be working? My interior lights are LED in series configuration. I robbed the Trace 4024 for use in low hour outages. It also helps with 110 amps battery recharging. Drok seems to make a decent Bucker. Mine is a custom unit made by an electronics engineer as a favor and the parts cost was close to 600 dollars 20 some odd years ago.

A towed rig clad with solar would be a heck of a lot easier to do than a motorhome. But mine can charge batteries at a 400 amp rate.

There are lots of ways to go including foregoing all 12-volt and going AC with the lighting. At the time Shur Flo wanted 300 dollars for a 24 volt water pump.

But it's that bopping down the road recharging that's perhaps the biggest challenge.

24-12 can be pretty cheap less than $100 for the 25A victron.....and the old converter can be retained both to use while on shore power to keep from cycling the battery bank AND for back-up in case of a bork'd DC converter

mlts22 wrote:
Other than needing to use a DC-DC converter for the 12 volt system, what problems would there be in going with a 24 volt battery bank for a custom rig?

The reason for this is that Magnum Energy has a PSW hybrid inverter which can run up to 4000 watts, as well as take two 120VAC power sources at the same time (genset and shore power.) However, for this functionality, it requires 24 volts in the battery system.

the mobile version (MSH4024M) only accepts one AC input. And the MS series which does have 2 inputs won't do load support (run partial from AC input and partially through the inverter)

on edit:

Also check the manual on that unit.....won't take both inputs "at the same time" it would be either or, can just be wired for both without having to switch a plug or have a separate transfer. Actually this is the reason the hybrid/mobile can only take one input......inverter is attached to one input already to provide load support, in which case the output IS getting both inputs

One big reason 24V is a good idea can be found in the specifications section of the inverter docs.....check out the page with the efficiency comparison between the 12V and the 24V version :B

MEXICOWANDERER wrote:
Using a generator for charging in conjunction with solar panels is viable. But failure of a 24-12 converter, isn't.

I could easily tap 12v off my bank until I could replace it, if such a thing would ever happen. Tag.

Using a generator for charging in conjunction with solar panels is viable. But failure of a 24-12 converter, isn't.

Ed_Gee wrote:
Perhaps the original poster's needs are different than mine and he can sufficiently operate with the inherent losses of a DC-DC converter ..

I know I can.

Vanner VANN-Guard 70-60 Series 60 Amp Battery Equalizer See original listing
Vanner-VANN-Guard-70-60-Series-60-Amp-Battery-Equalizer
Item Ended
Item condition:
USED USED USED USED USED USED USED USED
Ended:
Aug 01, 2015 , 12:02PM
Price:
US $350.00
Shipping:
$32.95 Expedited Shipping
Item location:
Cherry Hill, New Jersey, United States
Seller:
tubewinder (144 )
| Seller's other items


Out of my personal price range for sure. A 50DN oil cooled alternator is 500 dollars, used and abused. Since they have a 17 amp 28-volt field requirement and need an expensive voltage regulator AND ARE DIRECT ENGINE GEAR DRIVEN this narrows the useability a tad.

50DN air cooled is a cool 1,800 dollars USED and next to impossible to find without a fractured square stator hairpin winding. A replacement stator is 650 dollars.

The Niehoff on my bus cost $4,700 new. And weighs so much a cherry-picker is used for R&R. The Delcos are heavier yet. An 8 to 5 ratio pulley system on the Lombordini drives my air cooled 50 DN. Pretty serious and expensive stuff.

And finally in the late eighties after having the first and only five Vanner inverters go up in smoke within a couple of hours of being switched on, that I got from Transpo Electronics, Frank Oropeza, the owner got skittish and stopped handling them. They might have great buckers today, but five times burned...

I lean toward devices that have been proven. I do not know what high end manufacturers use such as Kountry Koach but I sure would investigate things before I plunged in.

Having a rig go useless, because of a unique product with no alternatives and no backup, does not turn me on. Unique? When you're 33 miles north of east -------, and the lights and water pump don't work and there is no help possible for 300 miles and then FedEx air or UPS next day are the only alternatives, this would make me wonder.

Chris Bryant wrote:
You don't need to convert 24 volts to 12 volts, you just use an equalizer http://www.vanner.com/manuals/EQUALIZER-70M-SERIES.pdf- it splits the battery banks in to 12 volt banks, and draws from the equally-

The Vanner VANN-Guard Power Management System is an efficient and highly reliable method of
obtaining a 12 volt DC power source from a 24 volt DC electrical system. The VANN-Guard makes the
batteries look like they are in series and parallel at the same time. In addition to providing regulated 12
volt power, the system ensures that battery voltages remain equal which significantly extends battery life.
Ideally suited for vehicle and alternate energy applications, the VANN-Guard is designed to save your
batteries and the money you would spend replacing them. Users of the Vanner VANN-Guard know that it
is the most cost effective and dependable solution for dual voltage systems.

.
Should be much more efficient than converting 24 to 12.

That's an interesting device, and should work pretty decently in this application. Internally, however, it technically is a 24V to 12V converter (with some control electronics thrown in). The diagram at the top of page 12 of the linked document (in regard to adding more 12V batteries) makes this rather more obvious, though it's also clear from a careful reading of the theory of operation.