aussiejohnny wrote:Interested to know more about that Terry. I have a small LA battery factory installed up the front of our van that i run a 24 - 12 dc dc sterling charger from the truck. There is a power wire from it to the rear of the van that powers the lights, slide outs etc.
Can i use it with this 'jerry can approach' to charge the lifepo4 battery pack while driving?
Also if travelling on a sunny day there should be no reason why the solar system can still be delivering charge?
You do need a method of switching the charging off if a cell reaches 3.6v but otherwise it will do the job fine.
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Kappy, you can buy a plug in usage meter on ebay for about $20, plug that into your inverter or grid supply and it will tell you how much you use over a day or whatever time you wish. That's what I do, because working out any other way is beyond me. I use a multimeter for testing what wire size to use, by connecting it up and testing the voltage output at the other end. I have a supply of different size wiring, which is sourced from the transfer station near us for free and that's allowed me to do lots of low voltage electrical things cheap. You can quickly see the voltage drops if any and change the wiring size, I find wiring extremely expensive so got this way to save.
Had my 120amp pack for 8 years, which was really expensive back then, used every day and some days it gets heavily used. My truck has a 15 amp 24-12v charger and that charges the lifepo5 pack, the bus has a 80amp 24v agm batteries charged by the bus alternator, via a redarc dual battery system. Then it goes through a 60amp 24v-12v charger which can charge the gel pack and 480 amp lifepo4, when I add my portable pack have 600amps of lifepo5 on board. The portable pack gets used on the house, cars, boat, bus truck, pumps and power tools. It's versatile and light, will post a photo of it over the next couple of days.
We also use small cell sizes of 40-50amps, they are cheaper, stay in balance easier and if you have a cell collapse, you can take it out and not lose much of your capacity. Cells 100amps or over, means if one has a problem, you can lose your entire system.
Unlike most others who use modified lead acid chargers, we use dedicated single stage 40amp and 60amp bulk mppt chargers, along with simple cell equalisers. Over the last 8 years and along with years longer experiences and knowledge of my late mates use of lithium, have developed a regime that holds up well. The voltage limits we use are 14v (3.5v per cell) upper and 12v lower (3v per cell) in a 12v system. Unlike lead acid, lifepo4 hates slow charge at it's upper voltages and that's when problems arise using float etc charging. Cells tend to become unbalanced when nearing 3.4v, yet from 3v to 3.4, they seem to have no problems and that's when bulk charging occurs in most systems.
With the system we use, the chargers work full on until 14v then switches off and each cell should sit at 3.5v. If there is no load, they settle back to 13.8v. With load, they switch off charging until the pack drops to 13.6, which means if you have enough charge coming in, it will be directed to load and your pack sits full for the night. There are lots of different approaches to this, which work for others.
Never have to watch my cells and the system is quite cheap, especially the equalisers which can now be bought on ebay for less than $100 I believe, This tends to happen when you design them, then get them made in china. It's not long before they are selling them in Aus cheaper than they could be imported and sold retail here.
Luckily it's not the came with chargers, the lead acid mob have a monopoly on supply, we had a really hard time getting someone to manufacture single stage bulk chargers. Manufacturers and resellers continue to claim float, absorb, equalisation and temp controls are fine in lifepo4 chargers. That's why they are claiming lifepo4 only last 5-8 years and that is true if you use lead acid charging regimes, as everyone on the road I've run into does.
Which ever way you go, you'll love what lifepo4 does for your life on the road, lead acid comes nowhere near them in any way, in my opinion and other forms of lithium although cheaper, come with safety issues. The only time I've seen lifepo4 have a problems was when someone accidentally drilled into a cell and the spark on the metal case, set the cell alight. All that happens I'm told is large amounts of smoke came out and then a flame, which was stopped by covering it. The rest of the pack was fine and I've seen the cell and pack involved, which is still in use.
Newcastle George wrote:Amps and amphours are two different things. Amps are current, not capacity.
George
Easiest way of deciding which term to use, amps and watts are instant power, Ah and Wh are power over time. 100 amps is how much the load is using, if it uses that for 1 hr then it can be said that the load for that period was 100Ah. The same 100 amp load for 30mins would use 50Ah.
Wh or watt hours are only easy to add up if the voltage is constant, battery voltage is never constant but generally 240vac is a reasonably constant 230vac, so watts shown on an electrical appliance can be divided by 12v for a lead acid battery and 13v for a lithium battery and a reasonably accurate figure plus 10% for inverter losses with indicate the instant load in amps being used from the battery. Multiply that by the number of mins the appliance is used, divide that by 60 and you will get a good idea how many Ah will be removed from the battery to supply the power to run that appliance.
An example is the induction cooktop. On full noise it will draw 2000w, from a lithium battery via an inverter 1000 x 10% =2200w / 13v = 170 amps. Sounds huge doesn't it, but in less than 4 minutes that would boil 2 ltrs of water, 4 x 2200w = 8800w minutes = 150Wh / 13 = 11.5Ah, 1 hrs output from 2 x 100w solar panel, doesn't sound like such a big thing when you look at it like that does it
Anyone who has much experience using an induction cook top will tell you full noise isn't used very much when cooking, the outside is burnt and the inside still raw if you try.
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Kappy, not only are flexible panels more expensive, but you have to stick them down and getting them off some time in the future may be a problem. Flat panels have an added bonus you may not have thought about other then being much cheaper, they can act as a tropical roof so you have an air gap between your roof and the panels. This lowers the temp inside as some heat is dissipated between the roof and panels.
bagmaker wrote:Is there a reason for the change Kappy?
Flexy panels have not got a great wrap so far.......... better to stick with the usual hard style if you can
I have 600 watts of 24 v panel and changing to 12 volt
Cheers
Kappy
Growing older is inevitable, growing up is optional.
My plastic backed flexibles have been a PITA to install, and have immediately developed defects after the first hot day. It appears to not extend to the outer surface... yet.
I'd take some convincing to repeat the decision, especially when Low Energy Developments have some only slightly larger 100W glass panels for $100 each delivered.
The 8 eyelet ones like those in the link mounted correctly seem to be as good as they get, but unknown if these panels are from the same factory or another factory knock off. We have been fitting ones that look similar for a while now and they have not been an issue, but how you mount them is critical, get it wrong and the panels fail.
If Vic off Road are willing to give you the 25 yr guarantee in writing I can't see you could loose, the rigid panel manufacturers don't offer anything better at a much higher price, the lower priced panels only carry a 12 mth guarantee at best. The difference between 3.5kg including mounting and Lexan v 13.5kg for the rigid per 100w means you can have almost 4 times as much solar on the roof for the same weight, add the benefits of the Lexan Thermoclear as far as heat insulation and you are way in front.
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
