The battery charging current on the AD-155C is actually limited to 0.2A... which is kind of a good thing, in that you won't have the situation Mark mentioned where the system won't start because the batteries are drawing too much current, but it is going to take a few weeks to completely recharge a 100ah battery.
On Tue, Jun 19, 2018 at 1:29 PM, <ch...@wbmfg.com> wrote: > Well, if the battery voltage eventually comes up to float voltage then you > have enough current. > There is a tiny amount of current needed to maintain the charge. > > *From:* Adam Moffett > *Sent:* Tuesday, June 19, 2018 12:23 PM > *To:* ch...@wbmfg.com > *Subject:* Re: [AFMUG] Battery Charging > > Sorry, that was not supposed to be offlist. Not used to the reply-all > thing yet. > -Adam > > On 6/19/2018 1:56 PM, Adam Moffett wrote: > > Something I've wondered about is whether there's a *minimum *charge > current. If you have something like a Meanwell AD-155C then you have a > whopping 155Watts to work with. If you have 100W of load then you have > 1amp of charge current. Then somebody maybe adds a couple of devices and > now you have 125W of load and maybe 1/2 amp of charge current. > > I won't be concerned if the problem is that it took a month to fully > charge, but is there a point where the charger is too weak and doesn't do > anything? > > I'm also not currently using a charger that small on such a large battery, > but in the past when I was doing everything on the cheap I've definitely > put a Meanwell AD-155C on a 100ah 48v battery to power a few Canopy units. > It worked fine, but I always wondered if I was hurting something by having > such a small charger. > > I'll definitely keep that 10-20% range in mind for the future, and thanks > for sharing. > > Thanks, > Adam > > > On 6/19/2018 1:11 PM, ch...@wbmfg.com wrote: > > OK, finally got that IEEE whitepaper to load. Nothing really new to me > but they did point out a few things I had not thought of for a long time. > The main points to consider are as follows: > > You need to have a rectifier/charger large enough to carry the load plus > produce no more than 20% of the battery capacity charge current. For > example, if you have a 100 Ah battery, you do not want to charge it more > than 20 amps. It is recommended that 10% or less be used to preserve > battery life. > > Too high of a charge current will shorten the battery life in a variety of > ways. Sealed VLRA batts are much more susceptible due to a reduced amount > of liquid electrolyte to serve as a heat sink. They also outgas thus > losing electrolyte and capacity during deep discharge. Furthermore they > have a chance of thermal runaway during heavy discharge or charge. Flooded > cells do not have this same problem. > > So, say you have a 48 volt system, your load current is 10 amps. You want > it to remain alive for 48 hours during a power outage. You need 24*4*10 = > 480 Ah of battery. Pretty large battery. $3500 or so. > > Now, after an outage you need to charge that battery and run your load. > So, 10% of 480Ah is 48 amps of charging current plus 10 amps for your > load. 58 amps of charger/rectifier. > > But wait, you really need to do N+1 for redundancy so two 60 amp > rectifiers would be needed. However then you have way too much recharge > capacity after outages that could damage your batts. > > So, you need to have rectifiers that will limit the current. The ones I > use allow you to set the whole shelf to limit the current. If you are > paralleling units that do not talk to each other, set each one for load > plus 5% of the battery. > > So in the above example, current limit the rectifiers to 34 amps each. If > one rectifier dies, the other can still pull the 10 amp load plus have 25 > amps for recharge. That will bring the batts back to fully charged in > about 19 hours. > > However if both are working, and there is an outage, when the power comes > back on there will be 68 amps of total current available. Take off 10 amps > for the load and you have 58 amps going into the batts. > > 58/480=12% You are golden. No battery damage. N+1 operation. All is > well. And you will recharge in about 10 hours. > > > > > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > >
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