2001 toyota camry 4 cyl base load?

I'm a volunteer EMT, and just purchased a 2001 Toyota Camry as my commuter. I need to add lights, siren, and 2-way radio to the car. It has the stock alternator, which (I believe) is 80A. I'm fairly particular about my installs (spent some time doing ambulance wiring for a few towns)... I was wondering if anyone has information on the base/stock electrical load on this car? I'm assuming, looking at the wiring diagrams and fuse sizes, that the 80A alternator doesn't have a whole lot of reserve capacity. But I'd like some actual numbers to back that up. I no longer have a DC clamp ammeter (haven't done installs for money in a while), and would like to avoid having to borrow one and then go through the turn on accessory, check ammeter cycle in the car (especially since nobody I know would have an ammeter that can do true RMS inside an engine compartment). Any advice/information would be helpful and most appreciated. Thanks, Jason

Usually voltage is used. If it drops below 14.4V or 13.8V etc... Current tells little - other than for dimensioning. But then mere DC current measurement is adequate. I'd use a $13 50A shunt ( here) and an ordinary DMM. (I use those to measure 250A starter motors.) Just measuring at idle or 1500 RPM should be an adequate "base load". Things like main lighting and audio can be calculated and added, but parking lights are worth measuring, and fans, and aircon etc - ok - everything except headlights. I'd probably assume a base of 20A otherwise.... (Alternators are sized for headlights with wipers and stop lights and...)

Thanks. Yeah, I'm interested in dimensioning - I need to know if the stock alternator will support my planned load before I start installing and wiring everything. I'm pretty picky (everything at or above emergency vehicle wiring standards) so it'll be utter hell if I get everything installed and wired and *then* realize the alternator can't support it. I'd done a bit of research, but assumed/read somewhere that most shunts will show false readings from the variable frequency/phase of alternator output, or from induced voltage. For some reason I'd thought that a true RMS current clamp was the only way to get realistic numbers...

RMS and AC is irrelevant - the loads cannot use it, and they tend to be so small in practice anyway. For determining creast factos and power factor of AC - yes, definitely, but not for vehicles DC circuits. The shunt will be fine. With DC DMM accuracy, you'll be within 2%. And that is far less than the output (and load!) variance with RPM and temperature.    As to knowing whether your alternator is big enough before hand, either you have to know the load exceeds is max output (ie, big loads are easy), else you have to know the profiles - ie, your average alternator output over your drive less cranking recharge plus all loads. (Or of course know that the alternator has more than enough headroom.) So do you plat that, or assume its new specifications? IE - an 80A alternator may only put out an average of 60A over a 30 minute drive. That's not easy - many plan and budget for an upgraded alternator and use a voltmeter to determine if it is needed.

Thanks for all of the advice. Understood about the first two points - for some reason, I'd been under the impression (from something I read, probably by someone who's not quite an authoritative source) that the AC would *greatly* throw off my readings. I'm asking around to see if I can find anyone with a DC clamp meter I can borrow... unfortunately the one guy I'd ask just moved out of state and the other electrician is on vacation for a week. Then again, I guess if I want to know what's going on during driving, I'm going to need the shunt... I'm probably going to need "more than enough headroom". I know the exact loads I'm going to be adding (at least their max rated, which is what I intend to plan for). I'm also planning for worst-case scenario, which is usually what I have: crank the car, within 30 seconds of cranking full rated draw on lights and siren. Absolute worst case (not that unusual) is what I just described for a *three minute* ride, then shut off. Mind you, the *smallest* vehicle I've ever wired like this was a Ford crown vic police interceptor with the 200A alternator... and a few Ford trucks with 240-300A.

oldspark wrote: As to knowing whether your alternator is big enough before hand, either you have to know the load exceeds is max output (ie, big loads are easy), else you have to know the profiles - ie, your average alternator output over your drive less cranking recharge plus all loads. (Or of course know that the alternator has more than enough headroom.) So do you plat that, or assume its new specifications?

How would I determine the cranking recharge? Honestly, I'm planning for absolute worst-case scenario - what I described above (short trip at full acc'y load), in the winter, with defrost, headlights, wipers, etc. I have a very strong suspicion the Camry alternator won't come close to what I need (I'm tentatively looking at a 46A load). As to voltmeter/figure it out then... I just don't deal with that very well. I've had 4 vehicles now that I've done similar installs on, plus doing a healthy bit of other people's vehicles, and work on a few ambulances. I'm pretty anal about designing things to industry spec, engineering the system, drawing up circuit diagrams, and then doing the install all at once, to written spec. Sorry for the long-winded reply. Thanks again for the advice. If I can get a clamp meter, I'm going to do measurements at a just-stated idle, planning for worst case. If not, I'll get a shunt.

Giddam Boss - these Rookies ask a lot. And they're smart too! HELP! Firstly to knock of a bit of an afterthought to my last reply: AFAIK, if any AC current were to be absorbed by the load(s), if that were only during one half cycle, that would be measured as a DC-offset plus the remaining (half-wave rectified) AC signal. IE - it is measured by a DC meter. And for the rest I assume an essentially balanced AC which cancels out +ve with -ve (graphical areas) - even though they aren't absorbed by the loads anyhow (only DC is). (Note - I see noisy DC as an AC signal with a DC offset.) With the history of your "smallest alternator" being 200A, I understand your concern. Don't you miss previous luxuries...? As to cranking, I usually sum it up as "a few minutes driving should replace most of the cranking charge", and by that I mean ~90% recovered. Whilst that may not factor in night or low-RPM driving, in most cases its seems fair - assuming a good battery, and normal OEM alternator overheads. [Ramble: People keep writing that the cheapest "cut to the bones" alternators are used. So what - if they put out the Manufacturers required current profile to cater for the worst idling on the rain at night on highbeam with full air-con and demisters...? An alternator must have overhead (spare capacity) for lights & wipers. That means at least (say) 40A above its rated baseload - long-term! It's not as if "economic" or cheap means an alternator without that implicit margin or overhead. ] But technically: cranking time x starter current. Can add "baseload" (IGN) if required, but better to treat that separately... You could then calculate AH or As used so you know how many Amp-Seconds/Hours are required plus an efficiency overhead (what is a battery's discharge:recharge efficiency - 70&? 95%?) - I usually add 30%. If you have battery discharge curves, you could more accurately estimate the battery's discharge by tracing down the discharge current = <whatever> Amps for n-seconds - the graph then shows what discharge that is equivalent to. Critical design will do that if needed: a batteries capacity varies a lot with the discharge (current) rate (eg, a 380AH C20 battery is a 200AH C5 battery, C20 & C5 = 20 & 5 hour "rated AH" discharge times.) But assuming normal vehicles, I reckon 5 minutes covers it. It may take more than tens of minutes to fully recharge, but that is minor. (If cut short, the next initial charge will be higher. If always too short or too low, then I (the battery) will die. RIP.) But yeah, the reality requires measurement. I'd "test" my system by idling with headlights on. If they don't dim compared to hi-RPM, then I have a great alternator.... (Dimming may be ok, but that's another story.) ...I know it handles, at idle, base + lights without dropping voltage (say 14.4V). Since alternator ratings are usually at normal or high RPMs, I feel confident I have much more "reserve" in normal diving. IE - at idle the alt may only output 40A compared to its rated 80A@2,500 engine RPM. Alas my dash voltmeter (3 digit LED) confirms the above, but without such equipment, the above is a damn good guess. And dimming may be ok - like if it's only at idle... The safe way is to add your load to the alternator and upgrade - ie, 80A + (tentative) 46A load = 126A => at least an 120A alternator. Or maybe 100A if your original had the headroom... Can you test with the load instead? Or add (46A x 12V =) 500W-600W of driving lights or fans? Unless it is a constant high 40+ Amps, your alternator might handle it. Assuming sunny day driving only, that load isn't much bigger than your lights & wipers... BTW - if later Camrys have larger alternators, they may fit. They might be using ND (Nippon Denso), but like other brands, the same alternator chassis may be used across various vehicles. A new release's alternator output may have been boosted, but it may have the same bracketing dimensions as the old. 6 years ago I was an alternator noob. I then found them simple: Usually a max of 3 (small-wire) connections (D+ or L charge lamp; S = Sense (battery+12V); IGN) though the ever-complicating IGN is now rare. I now run some 1995 80A alternator in place of my original 1960's system - 2 wires only (charge light & battery +12V) and it is one of many that fit the bracketry that I have. As I found - many fitted the same brackets - they tended to exist in families. By far the most standard was ND's "chassis tube" design - totally incompatible with others (well, sort of...). But find your "family" and then find the biggest version... Alas with stateside alternator prices seemingly well under half what we pay here, I they'd use catalog info instead of my dirty scribblings from countless cars at wreckers...